1. Field of the Invention
The present invention relates to a substrate treatment method and a substrate treatment apparatus.
2. Description of the Related Art
In fabrication processes of semiconductor devices, a resist coating treatment is performed in which a resist solution is supplied to, for example, a semiconductor wafer (hereafter referred to as a “wafer”) to form a resist film on the front face of the wafer.
This resist coating treatment is normally performed in a resist coating unit. The resist coating unit is provided with a nozzle for supplying a predetermined amount of the resist solution to the wafer. The nozzle is connected to a storage tank, which is a supply source of the resist solution, via a pipe. This pipe is provided with, for example, a pump for feeding the resist solution by pressure, a filter for removing impurities, an open/close valve for controlling discharge of the resist solution, and so on. These members constitute a supply mechanism of the resist solution. The resist solution in the storage tank is discharged from the nozzle via the pump, filter, open/close valve, and so on. In the resist coating unit, treatment is repeatedly performed in which the resist solution is supplied to wafers carried into the unit in succession.
By the way, in the resist coating unit, a pre-dispense of once draining the resist solution staying in the pipe via the nozzle has conventionally been performed before actual supply to a substrate. The pre-dispense in the prior art has been performed for the supply mechanism in the same system based on a single recipe and start condition. The reason why the pre-dispense has been performed based on the single recipe and start condition is to simplify control of the resist coating unit which normally has a supply mechanism in a plurality of systems.
However, there are a plurality of purposes of performance of the pre-dispense in the resist coating unit. The pre-dispense includes, for example, one performed at the time of change of lot for stabilizing the discharge amount of the resist solution from the nozzle, one for removing bubbles staying in the filter and pump, one for preventing drying of the nozzle and the like, and so on. The recipes including the discharge amounts of the respective pre-dispenses required for attaining these purposes and start conditions of the pre-dispenses are actually different from each other depending on their different purposes.
If it is desired to accomplish all the purposes of pre-dispenses by one kind of setting in the same supply mechanism as in the prior art, it is necessary to match, for example, regarding the frequency of pre-dispenses, the start condition to the setting of a pre-dispense which has a relaxed start condition, that is, which needs to be performed most frequently. The discharge amount also needs to be matched to the amount of a pre-dispense having the largest discharge amount among many pre-dispenses.
Besides, the resist solution coating treatment successively performed for wafers is performed in succession for every lot of substrates. When the supply of the resist solution to the wafer is stopped, the resist solution remains in the nozzle and the supply pipe. When left standing for a long time, the remaining resist solution dries or changes in quality. Therefore, a pre-dispense is performed at a break between treatments for lots of wafers as described above. Conventionally, the pre-dispense performed at a break between the lots has been performed uniformly every change of lot without fail.
During the pre-dispense, however, the treatment for wafers is suspended, and thus if its recipe is matched to that of the pre-dispense which needs to be performed most frequently, the throughput of the treatment is significantly decreased. Further, the resist solution discharged when the pre-dispense is normally disposed, resulting in increased amount of the resist solution going to waste. This problem also applies to the case in which the pre-dispense is performed every change of lot.